ABSORPTION AND LYMPHATIC TRANSPORT OF INTERESTERIFIED OR MIXED FATS RICH IN SATURATED FATTY-ACIDS AND THEIR EFFECT ON TISSUE-LIPIDS IN RATS

Interesterification of fully hydrogenated plant oils with liquid oils has been used as an alternative to partial hydrogenation to produce a zero-trans solid fat due to recent reports of unfavorable effects of d ietary trans fatty acids on serum cholesterol levels. Present study wa s carried out to examine absorption of saturated fatty acids derived f rom mixed and interesterified fats and their effects on concentration of serum cholesterol. Dietary fats consisted of tripalmitin or tristea rin: high oleic safflower oil: safflower oil ratios of 44.4:35.3:20.3 or their interesterified products; a melting point of the interesterif ied fat was lower than that oi the corresponding mixed fats. When rats were fed these-fat containing diets for three wks, absorption rate es timated by excretion of fatty acids into feces was higher in intereste rified fat-fed rats than in the corresponding mixed fat-fed rats. This improved absorption was accompanied by an increased concentration of liver triacylglycerols and an increased proportion of stearic acid in the adipose tissue and an increased propotion of oleic acid in serum a nd liver. Dietary fats exerted no significant effect on the liver or s erum cholesterol concentration or the excretion of neutral or acidic s teroids into feces. In contrast to dietary fat absorption, administrat ion of the mixed and interesterified fats, emulsified with taurocholat e and albumin, into stomach of rats cannulated with thoracic lymph duc t resulted in lymphatic triacylglycerols with a comparable transport r ate and with a similar fatty acid composition at each position of tria cylglycerols. These results demonstrate that interesterification impro ves absorption of dietary fats, possibly by facilitating emulsificatio n of saturated fats, but seems not to exert any adverse effects on the concentration of serum and liver cholesterol. (C) 1997 Elsevier Scien ce Inc.